Low slope ph electrode with charge transfer component

ABSTRACT

An aspect provides a low slope electrode device, including: a low slope measuring electrode for placement in an external sample solution, said low slope measuring electrode comprising: an electrode disposed within a glass container including an internal buffer solution and at least partially enclosing the electrode of the low slope measuring electrode, the glass container having two pH sensitive regions; an external buffer container including an external buffer solution and at least partially enclosing one of the two pH sensitive regions; and a separating element that separates the two pH sensitive regions; wherein: a first pH sensitive region of the glass container permits charge flow between the internal buffer solution and the external sample solution; a second pH sensitive region of the glass container permits charge flow between the internal buffer solution and the external buffer solution; the separating element, the first pH sensitive region, and the second pH sensitive region establish a charge flow circuit through the internal buffer solution, the external buffer solution, and the external sample solution; and the charge flow circuit acts as a voltage divider for the low slope measuring electrode. Other aspects are described and claimed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 13/832,685, filed on Mar. 15, 2013, the contents ofwhich are incorporated by reference in their entirety herein.

BACKGROUND

The subject matter described herein relates generally to devices andmethods for the measurement of a specific ion activity or concentrationin solution based on potentiometric sensors (potential difference orvoltage based measuring). An example of such measuring is use of a pHmeter to determine the pH of a solution.

In a potentiometric measuring system, meter circuitry is designed to usereadings of relative voltage, as sensed through measuring and referenceelectrodes, to calculate an ion concentration (hydrogen ionconcentration in the case of pH metering). Typically, a voltage issensed by an electrode measuring half cell and a voltage is sensed by areference half cell that are electrically connected to a suitablemeasuring meter (meter circuitry). It is well known that hydrogen ionconcentration in a given sample solution can be measured with such a pHmeasuring system.

In a conventional set up, reference electrodes (for example Ag/AgClelectrodes) are used together with measuring electrodes in a completecell. These reference electrodes and measuring electrodes may be used inconcert to determine ion concentration in a sample (for example, pH oranother ion). The reference electrode is designed in order to maintainits potential as constant as possible throughout the measuring process.In contrast, the measuring electrode is designed such that its potentialis a function of the concentration of the ion being tested. Constancy ofthe reference electrode's potential has been achieved by the presence ofa saturated electrolyte salt bridge or junction. The referenceelectrolyte leaks slowly through the junction. The relative potentialdifference between the reference and measuring electrodes may be used tocalculate the concentration of the ion in the sample, and may bedisplayed on a millivolt (mV) instrument (potentiometer).

The potential of a complete cell may be represented by:

E _(Cell) =E _(meas)−(E _(ref) +E _(j))

where E_(meas), E_(ref), and E_(j) are the potentials of the measuringelectrode, the reference electrode and the junction.

The electrode half cells (reference and measuring) are electricallyconnected to a pH meter circuitry to produce measurements in millivolts.The millivolt readings can be used to represent hydrogen ion activity inthe solution being measured. Such conventional systems and the partsthereof are well known to those skilled in the art and are available inthe commercial marketplace from various manufacturers such as HachCompany of Loveland, Colo. Thus, when the description set forth hereinreferences examples referring to conventional components such as pHglass, it is intended to mean a conventional component such as pH glassof the type which is sold in the commercial marketplace by Hach Companyof Loveland, Colo.

BRIEF SUMMARY

In summary, one aspect provides a low slope electrode device,comprising: a low slope measuring electrode for placement in an externalsample solution, said low slope measuring electrode comprising: anelectrode pairing, wherein a first electrode of the electrode pairing isoperatively coupled to a second electrode of the electrode pairing; aglass container including an internal buffer solution and at leastpartially enclosing the first electrode of the electrode pairing, theglass container having two pH sensitive regions; an external buffercontainer including an external buffer solution and at least partiallyenclosing the second electrode of the electrode pairing; and aseparating element that separates the two pH sensitive regions; wherein:a first pH sensitive region of the glass container permits charge flowbetween the internal buffer solution and the external sample solution; asecond pH sensitive region of the glass container permits charge flowbetween the internal buffer solution and the external buffer solution;the separating element, the first pH sensitive region, and the second pHsensitive region establish a charge flow circuit through the internalbuffer solution, the external buffer solution, and the external samplesolution; and the charge flow circuit acts as a voltage divider for thefirst electrode and the second electrode of the electrode pairing of thelow slope measuring electrode.

Another aspect provides a system, comprising: a low slope measuringelectrode for placement in an external sample solution, said low slopemeasuring electrode comprising: an electrode pairing, wherein a firstelectrode of the electrode pairing is operatively coupled to a secondelectrode of the electrode pairing; a glass container including aninternal buffer solution and at least partially enclosing the firstelectrode of the electrode pairing, the glass container having two pHsensitive regions; an external buffer container including an externalbuffer solution and at least partially enclosing the second electrode ofthe electrode pairing; and a separating element that separates the twopH sensitive regions; wherein: a first pH sensitive region of the glasscontainer permits charge flow between the internal buffer solution andthe external sample solution; a second pH sensitive region of the glasscontainer permits charge flow between the internal buffer solution andthe external buffer solution; the separating element, the first pHsensitive region, and the second pH sensitive region establish a chargeflow circuit through the internal buffer solution, the external buffersolution, and the external sample solution; and the charge flow circuitacts as a voltage divider for the first electrode and the secondelectrode of the electrode pairing of the low slope measuring electrode;at least one other measuring electrode; and a processor configured toutilize signals derived from the low slope measuring electrode and theat least one other measuring electrode device to produce a pHmeasurement output.

A further aspect provides a low slope electrode device, comprising: alow slope measuring electrode for placement in an external samplesolution, said low slope measuring electrode comprising: an electrodedisposed within a glass container including an internal buffer solutionand at least partially enclosing the electrode of the low slopemeasuring electrode, the glass container having two pH sensitiveregions; an external buffer container including an external buffersolution and at least partially enclosing one of the two pH sensitiveregions; and a separating element that separates the two pH sensitiveregions; wherein: a first pH sensitive region of the glass containerpermits charge flow between the internal buffer solution and theexternal sample solution; a second pH sensitive region of the glasscontainer permits charge flow between the internal buffer solution andthe external buffer solution; the separating element, the first pHsensitive region, and the second pH sensitive region establish a chargeflow circuit through the internal buffer solution, the external buffersolution, and the external sample solution; and the charge flow circuitacts as a voltage divider for the low slope measuring electrode.

The foregoing is a summary and thus may contain simplifications,generalizations, and omissions of detail; consequently, those skilled inthe art will appreciate that the summary is illustrative only and is notintended to be in any way limiting.

For a better understanding of the embodiments, together with other andfurther features and advantages thereof, reference is made to thefollowing description, taken in conjunction with the accompanyingdrawings. The scope of the invention will be pointed out in the appendedclaims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates a cross sectional view of an example low slopeelectrode device.

FIG. 2(A-B) illustrates a cross sectional view of example low slopeelectrode devices.

FIG. 3 illustrates a cross sectional view of an example low slopeelectrode device.

FIG. 4 illustrates a cross sectional view of an example pH measuringdevice having a low slope electrode device.

FIG. 5 illustrates a cross sectional view of an example pH meteringsystem having low slope electrode devices.

DETAILED DESCRIPTION

It will be readily understood that the components of the embodiments, asgenerally described and illustrated in the figures herein, may bearranged and designed in a wide variety of different configurations inaddition to the described example embodiments. Thus, the following moredetailed description of the example embodiments, as represented in thefigures, is not intended to limit the scope of the embodiments, asclaimed, but is merely representative of example embodiments.

Reference throughout this specification to “one embodiment” or “anembodiment” (or the like) means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment. Thus, appearances of the phrases “in oneembodiment” or “in an embodiment” or the like in various placesthroughout this specification are not necessarily all referring to thesame embodiment.

Furthermore, the described features, structures, or characteristics maybe combined in any suitable manner in one or more embodiments. In thefollowing description, numerous specific details are provided to give athorough understanding of example embodiments. One skilled in therelevant art will recognize, however, that various embodiments can bepracticed without one or more of the specific details, or with othermethods, components, materials, et cetera. In other instances,well-known structures, materials, or operations are not shown ordescribed in detail. The following description is intended only by wayof example, and simply illustrates certain example embodiments.

In conventional potentiometric measuring systems, reference electrodeshave many problems and it is desirable to remove, eliminate or otherwisere-design conventional type reference electrodes in potentiometricsystems. One attempt included treating pH sensitive glass to desensitizeit, thus permitting use of the electrode as a reference electrode evenif placed into the external sample solution. Unfortunately, this andother attempts have proven impractical.

Embodiments provide a low slope electrode by forming electricalimpedances in series such that a voltage divider is formed. Thus, thelow slope electrode device has reduced voltage sensitivity in terms ofmeasured voltage between an internal buffer solution and an external(sample) solution. Hence, a low slope electrode is produced and may beused in potentiometric metering systems, such as a pH meter.

Low slope electrodes, as described in connection with the exampleembodiments illustrated in the figures, when used in conjunction withother measuring electrodes, permits determining relative voltagepotential, and thus calculation of ion activity such as represented in apH value. By using measuring electrodes having different internal pHsolutions, electrode degradation over time may be compensated. Forexample, using a measuring electrode with an internal solution of pH 7,another measuring electrode solution of pH 4, along with one or moreother electrodes, as further described herein, permits compensating forelectrode degradation over time by comparison of measuring electrodeslopes, which are independent of sample pH.

An example of the calculation of a pH value from four electrode signals(for example, as provided by a device such as illustrated in FIG. 5) isgiven. Those skilled in the state of the art will observe that theequations shown give a basic method without every detail of computation.

pH Measurement Example

High slope electrodes (e.g., standard sensitivity pH electrodes) and lowslope electrodes (e.g., reduced sensitivity pH electrodes, as describedherein) may be used in pairs (e.g., two pairs of high and low slopeelectrodes with differing fill buffers, as illustrated in FIG. 5) formeasurement. The electrode pairs may also provide for drift compensation(e.g., as often encountered with aging pH probes). In terms of symbolsused in this example, U1 is the potential difference between the pair ofelectrodes with high pH buffer fill (e.g., pH 7). U2 is the potentialdifference between the pair of electrodes with low pH buffer fill (e.g.,pH 4). S1 is the difference of the two slopes, high and low, in the U1pair found at time of system calibration. S2 is the difference of thetwo slopes, high and low, in the U2 pair found at time of systemcalibration. pHH is the pH of the high pH internal fill buffer. pHL isthe pH of the low pH internal fill buffer. pHx is the pH of the externalsample solution (e.g., 115 of FIG. 5) the two electrode pairs measure.

Equations of Operation

The potentials U1 and U2 are given by:

U1=S1·(pHH−pHx);

and

U2=S2·(pHL−pHx).

These can be solved for pH in the well known way. pHx may be foundusing:

pHx=pHH−U1/S1;

and

pHx=pHL−U2/S2.

If the slopes S1 and S2 drift over time, e.g., S1→S1+dS1, and S2→S2+dS2,the pHx values calculated from the equations above will be in error. Ifthe drift of the two pairs is proportional, however, an accurate pH cannevertheless be calculated.

In the drifted state,

U1=(S1+dS1)·(pHH−pHx);

and

U2=(S2+dS2)·(pHL−pHx).

If the drift follows the assumption of proportionality, i.e.,(S1+dS1)/(S2+dS2)=S1/S2, then solving the above three equations gives:

pHx=(U1·pHL/S1−U2·pHH/S2)/(U1/S1−U2/S2),

where S1 and S2 are the slope values obtained at time of calibration. Inthe following description of example embodiments, various arrangementsare provided for establishing a low slope electrode for use in pHprobes.

EXAMPLE 1

In FIG. 1 is illustrated an example low slope electrode device 100. Theexample low slope electrode device 100 includes a lead wire 114 to anAg:AgCl electrode 101 bathed in an internal buffer solution 102 enclosedat the top, e.g., via epoxy region 111, in turn contained in a glasscontainer 120. The glass container 120 contains different elements,areas or regions. Glass container 120 contains pH glass elements 104,105, separated by insulating glass 108, that provide a voltage interfacefor the internal buffer solution 102 with the external buffer solution106 and the external sample solution 115, respectively. The pH glasselements 104, 105 each permit charge flow with a resistance/impedance,as does charge transfer component 107.

Thus, by inclusion of a separating element (in this example, the chargetransfer component 107 with an o-ring 112) a charge path is established(illustrated by dashed line in the figures) whereby charge moves in apath between the internal buffer solution 102, the external buffersolution 106, and the external sample solution 115. Electricalimpedances provided by the pH glass elements 104, 105, while notabsolute, is/are substantial relative to the essentially unimpededelectric path provided by the buffer and sample solutions. Thus,resistors are provided in series at least by the pH glass elements 104and 105 in the charge path. This forms a voltage divider to create a lowvoltage (V_(out), measured by the Ag:AgC electrode 101) relative to thevoltage between the external sample solution 115 and the internal buffersolution 102, forming an electrode having a “low slope” in comparisonwith a conventional measuring glass electrode (conventional pHelectrodes have a sensitivity of about 59 mV/pH unit). In a number ofembodiments a low slope electrode has sensitivity of less than thenormal pH glass electrode which is 59 mV/pH unit. In a number ofembodiments hereof, such a low slope electrode has a sensitivity ofabout ¾, ⅔, ½ or even lower than the “normal” pH glass electrodes. Thesensitivity may be modified as desired by providing different electricimpedances.

EXAMPLE 2

FIG. 2A illustrates the example of FIG. 1 in a slightly differentformat. Nonetheless, the pH glass elements 204, 205 of container 220,separated by insulating glass 208, and charge junction 216 form a pathfor charge flow with in-series impedances provided by the pH glasselements 204, 205, as illustrated and described in connection with FIG.1, allowing for reduced voltage, as sensed between measuring electrodes10 (VA) and 11 (VB) and 12 (VD) (measuring potential difference betweeninternal buffers 202, 206 and external sample solution 215).

In contrast, in FIG. 2B, a container 203 provides a pH glass element 205and an insulating glass 208 provides both impedances, again in series,in connection with a separating element (the external buffer container209). The insulating glass 208 prevents charge flow (essentially aninfinite impedance to charge flow), while the external buffer container209 acts as a separating element and divides the single pH glass element205 into two functional impedances in the charge flow path (againindicated by the dashed line). In FIG. 2(A-B), the potential VA-VD(measured by measuring electrodes 10, 12 and 11, respectively) providesa potential for the low slope electrode.

EXAMPLE 3

More than one piece or component may be used to form the impedances in aserial arrangement. For example, as illustrated in FIG. 3, a firstcontainer (or container element) 303 provides a pH glass element 305interface and electrical impedance between buffer (pHB, e.g., pH 7) andthe external sample solution 315. A second container 303, which may beidentical to the first container element, includes a second pH glasselement 305 and electrical impedance between internal buffer pHB (e.g.,pH 7) and external buffer pHB (e.g., pH 7, with the external buffer pHBbeing contained by the external buffer container 309 that also serves asa separating element), which is in turn connected to the external samplesolution 315 via a junction 316. Charge follows a path along the dashedline and an electrode measuring VA (as sensed by measuring electrode 10)registers reduced voltage due to pH glass elements 305 formingelectrical impedances in series (forming a voltage divider arrangement).As with Examples 1 and 2, the example two-piece low slope electrodedevice illustrated in FIG. 3 may be used in conjunction with a measuringelectrode in order to measure pH of an external sample solution 315. InFIG. 3, the potential VA−VB (as sensed by measuring electrode 10, 11)provides a potential for the low slope electrode.

EXAMPLE 4

As illustrated in FIG. 4, many arrangements are conceivable for forminga pH measuring device having low slope electrode(s) using impedances ina serial arrangement. For example, a low slope electrode is illustratedin FIG. 4 paired with a measuring electrode. A container 403 forming ameasuring electrode provides a pH glass elements 405 interface betweenbuffer internal thereto (e.g., pHB 7) and the external sample solution415, which registers a voltage (as sensed by measuring electrode 10). Amulti-component low slope electrode includes electrical impedances inseries via provisioning pH glass elements 404, 405 on container 420.Additionally, a external buffer container 409 (and junctions 416thereof) sets up a circuit loop, wherein charge flow between buffersolutions of container 420 (e.g., pHB 7 and salt bridge solution (SB)16) and external sample solution 415 is provided. The circuit loop isindicated by the dashed line in FIG. 4. Charge follows a path along thedashed line and the measuring electrode 12 registers reduced voltage (incomparison with measuring electrode 10) due to pH glass elements 404 and405 forming electrical impedances in series (forming a voltage dividerarrangement).

As with Examples 1, 2 and 3, the example low slope electrode device 400illustrated in FIG. 4 may be used in conjunction with a measuringelectrode, formed by container 403 in FIG. 4, in order to measure pH ofexternal sample solution 415. Appropriate buffering chamber(s) andsolutions may be employed to prevent adverse reaction between the saltbridge solution 16 and the process (external sample solution 415). Anexample salt bridge solution 16 may include 1M KCl. In FIG. 4, thepotential (VA−VD) difference between measuring electrodes 10, 12 andground electrode 15 provides a potential for the measurement of the pHof the external sample solution 415.

EXAMPLE 5

As an example of a potentiometric measuring system including low slopeelectrodes as described herein, a four electrode arrangement may beemployed to utilize the low slope electrodes (formed by containers 520)along with two measuring electrodes (formed by containers 503) tocompensate for electrode degradation over time. For example, in FIG. 5,one measuring electrode and one low slope electrode may be paired, e.g.,may each contain an internal buffer of a certain pH, for example 7.Similarly, another low slope electrode and another measuring electrodemay be paired, e.g., may each contain an internal buffer of a differentpH, for example 4.

In FIG. 5, the low slope electrodes are formed of a container 520including two pH glass elements 504, 505, enclosed using an externalbuffer container 509 and connected to the external sample solution 515via a junction element 516. A charge flow circuit is thereby establishedbetween internal buffers (e.g., pH 7) and the external sample solution515. Another low slope electrode is similarly formed but havingdifferent internal buffer solutions (e.g., pH 4). Measuring electrodesare appropriately paired with each low slope electrode (i.e., havingmatching internal/fill buffers, pH 4 and pH 7 as illustrated in FIG. 5).

As is known, a four electrode arrangement may provide signals to a meter514 (e.g., via AgCl electrode lines 51, 52, 53, 54) utilizing differingpH buffers to compensate/correct for changes (degradation) of electrodesover time. Thus, low slope electrodes commensurate with embodimentsdescribed herein (provided via containers 520 and related components inthis example) may be utilized in such a four electrode arrangement,along with a ground electrode 15 (for example, a piece of metal) in lieuof standard reference electrode(s). In FIG. 5, the potential provided bythe AgCl electrode lines 51, 52 and 53, 54 provide comparable potentialsfor the measurement of the pH of the external sample solution 515 andfor calibration over time.

Embodiments, as described in connection with the non-limiting examplesabove, provide a low slope electrode device by forming electricalimpedances in series such that a voltage divider is formed. Thus, thelow slope electrode device has reduced voltage sensitivity in terms ofmeasured voltage between an internal buffer solution and an external(sample) solution and may be exposed to the external sample solution.While not specifically illustrated, measurement of temperature of theexternal sample may be added by use of a standard component and used inion concentration calculations. Hence, embodiments provide a low slopeelectrode device that may be used in potentiometric metering systems,such as a pH meter.

For example, in FIG. 5, a potentiometric measuring system for measuringpH is illustrated, including electrode measuring assemblies and lowslope electrode assemblies. Each of the measuring and low slopeelectrode assemblies, as described herein, contain at least one pH glasselement 505. As described, the low slope electrode devices containvoltage divider arrangements, which may be formed using a container 520having two pH glass elements 504, 505. Each of the measuring and lowslope electrode assemblies may be connected (e.g., AgCl electrode lines51, 52, 53, and 54) to an amplifier (not shown) that acts to amplify theelectrical signals transmitted from the respective assemblies to themeter 514.

Generally, the signals are ultimately communicated to a potentiometricmeter circuitry, which includes components for measuring andextrapolating millivolt changes of the external sample solution in orderto provide a pH calculation. The meter circuitry may comprise aprocessor configured to utilize signals derived from at least one lowslope electrode device and at least one measuring electrode device toproduce a pH measurement output. This system differs from theconventional systems in that reference electrode half cells are omittedin favor of inclusion of the low slope electrode assemblies and ametal/ground rod. The operation of the example system illustrated inFIG. 5 is commensurate with the conventional and well known systemspresently in use (but having reference electrode half cells) andtherefore those skilled in the art will readily understand how theillustrated example system of FIG. 5 operates.

In the example system of FIG. 5 the measuring electrodes and the lowslope electrodes, which may be considered measuring electrodes as well,albeit with lowered ion sensitivity, may be calibrated with suitablebuffer solutions (for example, of pH 4 and 7) and a variable spananalyzer in accordance with methods already known for calibrating suchmeasuring cells before the system is put into actual use in a externalsample solution. In use, as the potentials sensed by the measuringelectrodes and the low slope electrodes change, these can be comparedagainst one another to provide a pH measurement which is equivalent tothe hydrogen ion activity in the external sample solution beingmonitored. The sensed potentials can be extrapolated by thepotentiometric meter circuitry to provide the hydrogen ion concentrationin the external sample solution by conventional means.

The various embodiments may be combined in a variety of ways. Forexample, in considering the example of a low slope electrodesillustrated in FIG. 5, i.e., arrangements using containers 520, itshould be noted that one may substitute the low slope electrodearrangement of FIG. 3 therefor. Thus, the low slope electrode of FIG. 3(formed of two containers 303) may take the place of container 520(formed of one piece of having two pH glass elements 504, 505), andlikewise another low slop electrode of FIG. 3 (formed of two containers303) may take the place of the other low slope electrode (formed of anadditional container 520 having two pH glass elements 504, 505) in FIG.5. The result is a six glass piece pH probe, with two low slopeelectrodes (of the form of FIG. 3) having four pieces in total, alongwith two high slope/normal sensitivity electrodes.

An advantage of such a six piece arrangement includes reduced cost ofcomponents, and reduced cost of the probe overall, even though morephysical components are utilized. This result flows from the low cost ofglass (and other components) used to form an arrangement such as in FIG.3 as compared to the cost of the glass used to form a low slopeelectrode of form illustrated in FIG. 5. The low slope arrangement ofFIG. 3 is lower cost by virtue of utilizing a container 303 having onlyone pH glass element 305 versus a container 520 having two pH glasselements thereon (504, 505). Thus, a six piece arrangement, as describedherein as a modification of FIG. 5 with low slope electrodes of FIG. 3,results in a lower cost pH probe having six identical containers of theform of container 303/503 (illustrated in FIG. 3 and FIG. 5,respectively).

This disclosure has been presented for purposes of illustration anddescription but is not intended to be exhaustive or limiting. Manymodifications and variations will be apparent to those of ordinary skillin the art. The embodiments were chosen and described in order toexplain principles and practical application, and to enable others ofordinary skill in the art to understand the disclosure for variousembodiments with various modifications as are suited to the particularuse contemplated.

Although illustrative embodiments have been described herein, it is tobe understood that the embodiments are not limited to those preciseembodiments, and that various other changes and modifications may beaffected therein by one skilled in the art without departing from thescope or spirit of the disclosure.

What is claimed is:
 1. A low slope electrode device, comprising: a lowslope measuring electrode for placement in an external sample solution,said low slope measuring electrode comprising: an electrode pairing,wherein a first electrode of the electrode pairing is operativelycoupled to a second electrode of the electrode pairing; a glasscontainer including an internal buffer solution and at least partiallyenclosing the first electrode of the electrode pairing, the glasscontainer having two pH sensitive regions; an external buffer containerincluding an external buffer solution and at least partially enclosingthe second electrode of the electrode pairing; and a separating elementthat separates the two pH sensitive regions; wherein: a first pHsensitive region of the glass container permits charge flow between theinternal buffer solution and the external sample solution; a second pHsensitive region of the glass container permits charge flow between theinternal buffer solution and the external buffer solution; theseparating element, the first pH sensitive region, and the second pHsensitive region establish a charge flow circuit through the internalbuffer solution, the external buffer solution, and the external samplesolution; and the charge flow circuit acts as a voltage divider for thefirst electrode and the second electrode of the electrode pairing of thelow slope measuring electrode.
 2. The low slope electrode device ofclaim 1, further comprising at least one additional electrode.
 3. Thelow slope electrode device of claim 2, wherein the at least oneadditional electrode comprises a reference electrode.
 4. The low slopeelectrode device of claim 2, wherein the at least one additionalelectrode comprises a measuring electrode.
 5. The low slope electrodedevice of claim 4, wherein the measuring electrode has a pH sensitivityof about 59 mV/pH unit.
 6. The low slope electrode device of claim 5,wherein the electrode pairing of the low slope measuring electrode has apH sensitivity of about ½ the sensitivity of the measuring electrode. 7.The low slope electrode device of claim 1, wherein the first pHsensitive region of the glass container and the second pH sensitiveregion of the glass container are separated by insulating glass.
 8. Thelow slope electrode device of claim 1, wherein the first pH sensitiveregion of the glass container and the second pH sensitive region of theglass container are formed of pH glass.
 9. A system, comprising: a lowslope measuring electrode for placement in an external sample solution,said low slope measuring electrode comprising: an electrode pairing,wherein a first electrode of the electrode pairing is operativelycoupled to a second electrode of the electrode pairing; a glasscontainer including an internal buffer solution and at least partiallyenclosing the first electrode of the electrode pairing, the glasscontainer having two pH sensitive regions; an external buffer containerincluding an external buffer solution and at least partially enclosingthe second electrode of the electrode pairing; and a separating elementthat separates the two pH sensitive regions; wherein: a first pHsensitive region of the glass container permits charge flow between theinternal buffer solution and the external sample solution; a second pHsensitive region of the glass container permits charge flow between theinternal buffer solution and the external buffer solution; theseparating element, the first pH sensitive region, and the second pHsensitive region establish a charge flow circuit through the internalbuffer solution, the external buffer solution, and the external samplesolution; and the charge flow circuit acts as a voltage divider for thefirst electrode and the second electrode of the electrode pairing of thelow slope measuring electrode; at least one other measuring electrode;and a processor configured to utilize signals derived from the low slopemeasuring electrode and the at least one other measuring electrodedevice to produce a pH measurement output.
 10. The system of claim 9,wherein the at least one other measuring electrode has a pH sensitivityof about 59 mV/pH unit.
 11. The system of claim 10, wherein theelectrode pairing of the low slope measuring electrode has a pHsensitivity of about ½ the sensitivity of the at least one othermeasuring electrode.
 12. The system of claim 11, wherein the at leastone other measuring electrode comprises two measuring electrodes eachhaving a pH sensitivity of about 59 mV/pH unit.
 13. The system of claim12, wherein: one of the two measuring electrodes comprises a fill bufferof about pH 4; and another of the two measuring electrodes comprises afill buffer of about pH
 7. 14. The system of claim 13, wherein the twomeasuring electrodes act as a measuring pair.
 15. A low slope electrodedevice, comprising: a low slope measuring electrode for placement in anexternal sample solution, said low slope measuring electrode comprising:an electrode disposed within a glass container including an internalbuffer solution and at least partially enclosing the electrode of thelow slope measuring electrode, the glass container having two pHsensitive regions; an external buffer container including an externalbuffer solution and at least partially enclosing one of the two pHsensitive regions; and a separating element that separates the two pHsensitive regions; wherein: a first pH sensitive region of the glasscontainer permits charge flow between the internal buffer solution andthe external sample solution; a second pH sensitive region of the glasscontainer permits charge flow between the internal buffer solution andthe external buffer solution; the separating element, the first pHsensitive region, and the second pH sensitive region establish a chargeflow circuit through the internal buffer solution, the external buffersolution, and the external sample solution; and the charge flow circuitacts as a voltage divider for the low slope measuring electrode.